1. Field of the Disclosure
The present disclosure relates generally to fluid ejection devices for printers, and more particularly, to a method for fabricating a fluid ejection device.
2. Description of the Related Art
A typical fluid ejection device (printhead) for a printer, such as an inkjet printer, includes a substrate (silicon wafer) carrying at least one fluid ejection element thereupon; a flow feature layer configured over the substrate; and a nozzle plate configured over the flow feature layer. The nozzle plate and the flow feature layer of the fluid ejection device are generally formed as thick layers of polymeric materials. Further, the fluid ejection device includes a drive circuitry layer that may be made using complementary metal-oxide-semiconductor implantation. Such a drive circuitry layer is electrically coupled with the at least one fluid ejection element, and assists in electrically connecting the fluid ejection device to the printer during use.
FIGS. 1-8 depict a typical process flow for fabrication of a fluid ejection device 100 (as depicted in FIG. 8). FIG. 1 depicts a substrate 110 having a top portion 112 and a bottom portion 114. FIG. 2 depicts formation of a drive circuitry layer 130 on the substrate 110. Subsequently, fluid ejection elements 150, 170 are fabricated on the top portion 112 of the substrate 110, as depicted in FIG. 3. Each fluid ejection element of the fluid ejection elements 150, 170 is electrically coupled to the drive circuitry layer 130. Thereafter, the substrate 110 is subjected to grinding from the bottom portion 114 thereof up to a predetermined height, ‘H1’ (referring to FIGS. 2 and 3). Subsequently, a planarization layer 190 (polymeric layer) is formed over the top portion 112, and particularly over selective regions (not numbered) of the top portion 112 of the substrate 110, as depicted in FIG. 4. Thereafter, exposed regions (not numbered), i.e., without any planarization layer 190, of the top portion 112 of the substrate 110 are etched using Deep Reactive Ion Etching (DRIE) technique to configure at least one slot, such as slots 116, 118, within the top portion 112 of the substrate 110, as depicted in FIG. 5. Each slot of the at least one slot serves as a fluid via of the fluid ejection device 100.
Subsequently, a layer 210 of an etch-stop material is then deposited over the exposed regions of the top portion 112 of the substrate 110 while filling the slots 116, 118 with the etch-stop material, as depicted in FIG. 6. Thereafter, the bottom portion 114 of the substrate 110 is etched to configure at least one fluid feed trench, such as a fluid feed trench 120, within the bottom portion 114 of the substrate 110, as depicted in FIG. 7. The fluid feed trench 120 is in fluid communication with the slots 116, 118. Subsequently, the layer 210 of the etch-stop material is removed from the top portion 112 of the substrate 110. Thereafter, a nozzle plate 230 (photo-imageable layer) is formed over the planarization layer 190. The planarization layer 190 serves as the flow feature layer of the fluid ejection device 100.
However, such a method of fabricating fluid ejection devices is incapable of allowing aggressive post-DRIE clean-ups, in order to avoid any damage to the flow feature layer. Specifically, available DRIE etching processes and strip methods are limited by the presence of the flow feature layer and the necessity of keeping the flow feature layer intact for permanent bonding of the nozzle plate. More specifically, clean-ups after DRIE etching processes may affect the adhesion of the nozzle plate to the flow feature layer. Further, performing DRIE etching processes post formation of the flow feature layer has also facilitated corrosion (manifestations such as ink ingression) of the fluid ejection devices.
In addition, application of DRIE etching processes that employ hydrophobic polymers in masking and passive layers proves to be unsuitable, as the hydrophobic polymers are difficult and expensive to remove. Thus, many prior art methods that employ such DRIE etching processes for fabricating fluid ejection devices are cost-ineffective.
Accordingly, there persists a need for an efficient and a cost-effective method for fabricating fluid ejection devices for printers without causing any damage to flow feature layers and nozzle plates of the fluid ejection devices.